During WW2 the Great Northern built box cars with plywood sheathing. They are probably often mistaken for steel.
Did any other railroads have plywood cars[?]
The Great Northern also had plywood cabooses. During WWII the government used plywood for PT boats if memory serves.
Dave Nelson
The Frisco also added plywood sheathing to several of it’s rebuilt boxcars. The NYC experimented with plywood too, but only sheathed a number of their cabooses with it with any regularity. I think many roads tried plywood after WWII, but mostly started dumping wood cars in favor of newer steel AAR or P-S boxcars. Plywood didn’t hold up too well out in the open, especially with the relatively poor paints available before the 1960s.